In a medium bowl, stir together flour, baking powder, baking soda, and salt. In a large bowl, using an electric mixer, beat 6 tablespoons butter on high until light and fluffy. Add granulated sugar and beat until well combined. Beat in eggs, one at a time, scraping down bowl as needed. Beat in vanilla. With mixer on low, add flour mixture in three additions, alternating with two additions yogurt, and beat to combine.

With a spatula, spread batter over nectarines. Bake until cake is dark golden brown and a toothpick inserted in center comes out clean, approx 45 minutes. Let cake cool in pan on a wire rack, 15 minutes. Run a knife around edge of pan and invert cake onto a serving plate. Garnish with the hickory nuts & serve warm. We also buried this beauty in piles of vanilla ice cream!